Electroluminescent (hereinafter EL) phosphors are used for backlighting in LCD's, in copying machines, for backlighting membrane switches, for automotive dashboard and control switch illumination, for automotive exterior body lighting, for aircraft style information panels, for aircraft information lighting, and for emergency egress lighting. U.S. Pat. Nos. 3,014,873; 3,076,767; 4,859,361; 5,009,808 and 5,110,499 relate to methods for producing EL phosphors. Since EL phosphors are sensitive to moisture it is not uncommon for the phosphors to be coated with a moisture-resistant coating of a metal oxide such as alumina. Such coating processes have involved reacting the phosphor, via a chemical vapor deposition process, with a coating agent such as, for example, trimethylaluminum and water vapor. An example of such a coated phosphor is shown as Sample Number CJ564 in TABLE I and as CJ30 in TABLE II. The phosphor coating, in the first instance, contains 4.4 weight percent (hereinafter wgt. %) aluminum, has a Y color coordinate of 0.199 on the C.I.E. Chomaticity Diagram (X value, 0.158) and a half-life of 195 hours and, in the second instance, 4.0 wgt.% aluminum, a Y value of 0.203 and a half-life of 256 hours. As used herein the half-life refers to that period of time when the brightness of the phosphor decreases to ½ of its brightness at 24 hours.
A different coating process having many advantages over the TMA/water process comprises reacting a coating agent such as TMA with an oxygen-ozone mixture. This latter process is water-free; however, in some instances this process produces undesired emission changes in the phosphor. Even though such phosphors have achieved some commercial success in areas where, for example, brightness might be more desirable than a particular emission spectra, it would be an advance in the art to provide a process for achieving a desired emission spectra in a phosphor having a moisture-sensitizing coating applied by an oxygen-ozone process.